Allow option to keep the containers alive

It would be nice to keep the docker containers alive for speeding up the test runs. Now, in every test run containers are re-created and can't keep them alive since this block

  def __del__(self):
        """
        Try to remove the container in all circumstances
        """
        if self._container is not None:
            try:
                self.stop()
            except:  # noqa: E722
                pass

removes containers when the instance variable is deleted (when the program terminates) and I cannot override it because this also runs without using with as block.

I don't want my Mysql container to be recreated everytime. I am running tests very frequently and I am waiting couple seconds everytime. Pretty annoying.

I can make a small PR if that makes sense?

首先阅读 del 方法附近的 testcontainers/core/container.py，并跟踪测试运行结束时容器如何停止，包括在 with 块之外的使用。定义该选项对于上下文管理的容器和直接创建的容器的生命周期行为；完成的标准是调用方可以让 MySQL 容器在多次运行之间保持存活，而不会自动清理。